Chemical process



Sept. 19, 1944. c. E. HEMMINGER 5 ,5

CHEMICAL PROCESSY Filed April 9,1 1941 0 Tz ICTlO/IATING. 1 TOWER O O O (OK/1V6 .DRUM

max/a TOR FZAqT/O/VATING l/EA T/ 'G rowan c all.

.SOLVEN 7' TREA T52.

76 MASH/#6 TOWER Patented Sept 19, 1944 CHEMICAL PROCESS.

Charles E. Hemminger, Weatfield, N. 1., assignor to Standard Oil Develo poration of Delaware pment Gompany, a cor- Application April 9, 1941, Serial No. 387,583 (01. 196-55) The present invention relates to the art of treating hydrocarbons and, more particularly, it relates to the art of obtaining from relatively heavy or high-boiling hydrocarbon oils increased quantities of fractions boiling substantially within the gas oil range.

As is generally known, ordinarily, the first refinery operation in treating a crude petroleum oil to obtain commercially valuable constituents thereof is to subject it to simple distillation or topping to remove from the crude oil those constituents boiling up to and including the socalled gas oil range, that is to say, those constituents are removed, by distillation, which boil up to about 700-850 F. The residue, of course, contains constituents which may be processed to recover valuable constituents such as lubricating oil, parailin wax, petroleum asphalt, and the tion ordinarily is not considered as good a feed stock as that produced by viscosity reducing, for a catalytic cracking operation, since the former is quite apt to. contain appreciable quantities of naphthalene, anthracene, phenanthrene, benzanthrene, and other cyclic hydrocarbons containing a plurality of benzene rings in a single nucleus. These multi-ring' aromatic compounds tend to produce excessive amounts of coke on the catalyst in a catalytic cracking operation. Moreover, to 35% of gasoline is produced and it like, depending uponthe nature and origin of the original crude. There are, however, occasions when a reduced crude or topped crude, due to commercial demand or for some other reason, is processed to recover additional quantities of gas oil, heating oil, fuel oils, and the like.

In current practice there are at least two general methods for processing reduced or topped 'crudes to recover additional quantities of gas oil has a low octane number. It is desirable to produce a minimum of gasoline in either of these two thermal operations to have the highest final octane number on the crude when using catalytic cracking of gas oils.

1 have discovered a means of treating a reduced petroleum crude operation which, in its broader aspect, involves first subjecting the reduced crude to a viscosity-breaking operation in the presence of a powdered carbonaceous material and thereafter subjecting the tar bottoms from the viscosity breaking operation to a coking operation.

aromatic hydrocarbons having more than, two

benzene rings in a condensed nucleus. The viscosity reducing operation also produces a petroleum tar and heavy oil which may be further heat treated to produce asphalts and road paving compositions or sold as a liquid fuel oil. The thermal treatment of the heavy constituents of the residuum partially cracks it and reduces its viscosity. As a'resuit less gas oil is necessary to blend therewith for a fuel oil of saleable viscosity.

The second method, the coking of reduced crudes, is a much more drastic heat treatment of the reduced crude than is the vis-breaking operation since it results usually in the production A of volatilizable hydrocarbons such as gas oil, gasoline, and light hydrocarbons, together with a solid coke. The gas oil from the coking opera- I have found that I obtain increased quantities of gas oil from the viscosity breaking operation,

which gas oil has excellent qualities as a feed stock for a catalytic cracking operation. In the coking operation, I, of course, produce a gas oil which is not, as such, particularly suitable for catalytic cracking but may however be employed as a feed stock in a thermal cracking operation. According to my present process I may subject the gas oil from the coking operation to a treatment with solvents such as S0: wherein I am enabled to improve the quality of the gas oil by leum'oil into gas oil of a quality suitable for use as a catalytic cracking stock.

Another object, of my invention is to reduce the viscosity thereof, to produce a gas oil, a relatively heavy hydrocarbon oil in the presence of a granulated or subdivided carbonaceous material such as petroleum coke and thereafter to coke the tar and heavy oil from the viscosity reducing operation to produce a further quantity of gas oil, the

added coke being present also in the coking operation.

A further object of my invention is to subject a heavy petroleum oil residuum to viscosity reducing in the presence of added granular petroleum Other objects and advantages of my invention will more fully appear hereinafter.

Th present invention is fully disclosed in the following specification and claims, reference being had to the accompanying drawing.

Fig. 1 shows a diagrammatic flow plan serving to indicate a preferred modification of my present improvements.

Referring in detail to the drawing, an East Texas crude oil of about 38 A. P. I. gravity is introduced into the system through line I and thence discharged into a coil 3 disposed in a suitable furnace setting 5. The oil is heated in coil 3 to a temperature within the range of from about 500-900 F., under a gauge pressure of 5 to 500 lbs/square inch, whereupon the heated oil is withdrawn from coil 3 through line 3 and thence discharged into fractionating tower 8 from which overhead products containing gasoline and gas are withdrawn through line I0 and heavy naphtha and gas oil through side streams 9 and II as separate products for sale as such or further processing.

The heavy oil bottoms separated in drum 8 which may, for example, have an initial boiling F. and a gravity of 18 A. P. I. are l2 and discharged into a second Just point of 700 withdrawn through line through injector l9 and pump 2| heating coil ll disposed in a furnace l5.

prior to discharge of the oil in line l2 into coil l4, petroleum coke having a particle size of from say 100 to 400 mesh is withdrawn from a feed hopper l6 through a star feeder I1 and a conduit l8 and thence fed into mixing means I9 to form a slurry of coke and oil. The amount of coke thus added'may vary in rather wide limits, say 1 to 100 parts by weight of coke per 100 parts of oil, with 5 to 50 parts preferred. The oil is heated in coil to a temperature of from about 800 F. to 1000 F. while maintainingal-coil outlet pressure of from 1 to 1000 lbs/square inch gauge. The oil feed rate to the coil may vary from 1 to vol. of oil per vol. of coil per hour. The oil is withdrawn from coil I through line 20 and discharged into a second separation drum 25. The vapors containing gas oil and light products are withdrawn from separation drum 25 through line 28' and may be delivered to a fractionating tower 29 from which normally gaseous hydrocarbons and gasoline are withdrawn through line 32 while a gas oil fraction is recovered through line 34.

of from about 900 F. to 1100 F. This coil is merely a preheating coil and the temperatures indicated are attained as rapidly as possible, say from to 10 minutes being sufiicient time of residence of the oil in the coil to acquire said temperatures. The oil is withdrawn from coil 36 through line 40 and discharged into a coking drum43. To attain continuity, it will be readily understood by those skilled in this particular art, that two or more coking drums should be employed so that while one or more are being decoked, the other or others maybe employed in the on-stream operation. The oil is subjected to the temperatures indicated, namely, 800 F. to 1100? F., and preferably to a superatmospheric pressure which may be as high as 750-1000 lbs/square inch. Drum 43 may be a simple upfiow drum for coking or it may be any other form of coking apparatus such as a heated coil, continuous coker producing a powdered coke, refractory hearth coker or other types known to the art. The vapors are withdrawn from the coking drum through line 46 and delivered' into a fractionating column48. Several fractions may be recovered from fractionating column 48, such as gasoline and higher hydrocarbons through line 50, domestic heating oil through line 52, and a heavier oil through line 55. The bottoms from the tower may, if desired, be recycled through line 58 to line 30 for further treatment, or may be withdrawn through line 60 and processed to recover desired products such as heating fuels.

Preferably, the gas oil recovered through line from tower 48 is treated with a solvent such as liquid $02, in a suitable tower 62, the S02 being supplied through line 80. A rafiinate substantially free of aromatics containing two or more benzene rings in a condensed nucleus is recovered from treating tower 82 through conduit 64 to still 66, subsequently discharged through line 68 to tower 10 to be washed with an alkaline substance such a aqueous sodium carbonat or caustic soda, and thence pumped by pump 12 through transfer line H to line 35 where it admixed with the gas oils previously produced as hereinbefore explained.

The washing solution may be discharged into tower 10 through line 18 and removed through line 19.

The S0: associated with the raffinate is recovered from still 66 through line 16, compressed and refrigerated in 18 and recycled through line 80 to treating vessel 62.

The virgin gas oil recovered from fractionating tower 8 through line H may be combined with that in line 35 and the combined gas oils may be delivered to storage (not shown) {as a suitable source of supply for a catalytic cracking feed stock. The presence of the fine powder in the vis-breaking operations allows higher operating temperatures and shorter contact times than heretofore employed in vis-breaking since carbon formation in the tubes is prevented by the scrubbing action of the coke particles and their absorptive properties for asphaltic material in the tar.

The heavy oil containing the added coke is withdrawn from drum 25 through line 30 by means of pump 3| and discharged into a third coil 36 disposed in a furnace setting 31 where the oil is heated to temperatures within the range Meanwhile, the extract formed in tower 62 may be withdrawn therefrom through line 85. This extract may be freed of SO: and the hydrocarbons may be treated to produce more or less high-powered solvents since they contain aromatics, or the hydrocarbons may be employed for some other suitable purpose.

The solvent treatment herein described is an incident of my complete process, and as such, does not involve invention by me, since I may employ any conventional solvent treating technique and any known solvent.

v Referring again to separator 25, if some of the finer particles of coke are carried overhead through line 28, the vapors are preferably delivered to one or more cyclone separators to remove suspended or entrained coke. Also a portion of the coke formed in the process may be ground and reintroduced into the system through hopper Hi. It will be understood, of course, that coke from some extraneous source may be added to the oil in line II, that is coke from some proc- I ess other than the on just now described, or even coke derived from destructive distillation of .coal may be employed. It may also be desirable to add the coke to mixer l9 at an elevated temperature so that a portion of th heat required could be obtained by heat transferfrom the coke. Furth ermore, superheated steam may be em- Ployed to assist in the heating of the oil in coils 3, l4 and 36 and the vaporizations in drums 25 and 43.

While it is normally desirable to fractionate the products from coke drum 43 separately to give desirable products, th vapor from drum 43 may be introduced by line 41 into line 20 and tower 48 is not used. Under these conditions the vapor products from both the viscosity breaking and the coking operations issue from 25 through line 28. The temperature and pressure in tower 25 may be varied so that controlled amounts of gas oil introduced in the vapors in line 20 are withdrawn through line 28 or withdrawn through line 30 for coking. The vapors in line 28 may be taken directly to a catalytic cracking unit or may be fractionated in tower 29 to give gas, gasoline and/or light gas oil overhead in line 32 and gas oil in line 34 for feed to catalytic cracking unit.

Moreover, the described combination of viscosity reducing and cokinghas advantages over one step coking of the residuum even where the untreated gas oils from the two operations are combined (i. e. where the gas oil from the coker 43 is not treated with a solvent). In the single step coking operation about 30 gallons of low octane number gasoline are produced from 100 gallons of original residuum. In the two step operation only gallons of gasoline are produced, leaving about 40 gallons of pitch to be coked. The gasoline in the latter operation is 12 gallons, making a total of 22 gallons of low octane gasoline in the Feed-18% East Texas residuum Viscosity One Coking reducing stage plus coking Although the combination operation (without solvent treatment) has been discussed as a source of gas oil for catalytic'cracking, the gas oil, separate or mixed, may also be used for thermal cracking. In the latter case, the higher aniline point, 195 F. as against 166 F. of the combination operation indicates a more parafilnic stock which gives a. higher'yield in thermal cracking.

other uses as heating oils and Diesel fuels. The decreased coke and low octane number gasoline yields are corollary advantages. Moreover, the

volume of the expensive coke drum and attendant equipment is decreased by the absence of the vapors produced'in the viscosity reducing operation.

To review briefly, the present invention relates primarily to a process of preparing a feed stock for a catalytic cracking operation and is characterized by the features of viscosity reducing, followed by coking, of a heavy petroleum oil in the presence of powdered coke, or the like, the powdered coke being rather finely ground and having as a. particle size below 20 mesh. The presence of the coke in the viscosityreducing operation improves the yield and quality of the gas oil from the standpoint of a catalytic'or thermal cracking feed stock, and substantially all of the coke which is added to the process is finally withdrawn from the viscosity reducing zone with the tar. Hence, it is desirable to coke the heavy oil and tar rather than to attempt to process it to form asphalt or road paving compositions, since tar and asphalt should be free from hardened particles of coke.

Many modifications of my invention falling within the spirit and scope thereof will suggest themselves to those who are familiar with this art.

What I claim is:

1. In a process for producing gas oil suitable for cracking operations from heavy petroleum residual crudes, the steps which comprise vis c'osity breaking the reduced crude by passing it through a long, narrow, heated conduit along as a charging oil to a catalytic cracking operation which comprises subjecting a heavy and residual petroleum oil to a viscosity reducing ope'ration in the presence of divided coke, recovering a quantity of gas oil from the viscosity reducing operation, subjecting heavier oil and tar residue, remaining after removal of said gas oilfrom the products of the viscosity reducing operation, to a coking operation to produce a further quantity of gas oil, treating the said gas oil with a selective solvent to remove aromatic hydrocarbons from said gas oil, and combining the gas oil produced in the coking operation, after removal of the aromatics, with the gas oil'produced during the viscosity breaking operation. CHARLES E. HEMMINGER.

Of course, the gas oils are a superior product for Q 

